The diameter is about 1 and 7/8th inch. Winds up, ticks and keeps time. Space on the back for engraving! (see photos)
 The diameter is about 1 and 7/8th inch

New Haven, better known for its clocks than its watches, was formed in 1853 and began to offer non-jeweled pocket watches about 1880. Small back-wind clock movements were placed in large watch cases; so, they were really as much clock as watch. New Haven expanded their watch manufacturing in the early 1900's and continued to make watches until the early 1940's when they converted all production to the war effort. Production resumed after the war but the company never really made a go of it. The company had been taken over by the Rensie Watch Co. of NY, which represented Swiss watchmaking interests. Under Swiss control the financial situation steadily deteriorated, and by 1959 continuation was no longer viable and the company folded